In Hebrew M. Maimonides calls it the two-lettered name, and derives it from the Tetragrammaton, of which he says it is an abbreviation. Others have denied this, and assert that Jah is a name independent of Jehovah, but expressing the same idea of the Divine Essence. It is uniformly translated in the authorized version of the Bible by the word Lord, being thus considered as Synonymous with Jehovah, except in Psalm lxviii, 4, where the original word is preserved: "Extol Him that rideth upon the heavens by His name Jah," upon which the Targum comment is "Extol Him who sitteth on the throne of glory in the ninth heaven; Yah is His name." It seems, also to have been well known to the Gentile nations as the triliteral resume of God; for, although biliteral among the Hebrews, it assumed among the Greeks the triliteral form, as IAO Macrobius, in his Saturnalia, says that this was the sacred name of the Supreme Deity; and the Clarian Oracle being asked which of the gods was Jao, replied, "The initiated are bound to conceal the mysterious secrets. Learn thou that IAQ is the Great God Supreme who ruleth over all".
- Source: Mackey's Encyclopedia of Freemasonry